With the continuous development of the semiconductor integrated circuit (IC) technology, the critical dimension (CD) of semiconductor devices and interconnect structures has become smaller and smaller. Thus, the distances between metal lines of the interconnect structures have been continuously reduced; and the dielectric layer used for isolating the adjacent metal lines has also become thinner and thinner. Accordingly, crosstalk between adjacent metal lines occurs. Reducing the dielectric constant of the dielectric layer is able to effectively reduce the crosstalk between adjacent metal lines. Further, the low dielectric constant (low-K) material is also be able to reduce the RC delay between metal interconnect lines. Thus, the ultra-low-K (ULK) dielectric material has been more and more widely used as the dielectric layer in the metal interconnect structures.
An existing process for forming a metal interconnect structure in a ULK dielectric layer includes forming an ULK dielectric layer on a substrate; etching the ULK dielectric layer to form a trench; and forming the metal interconnect structure in the trench. The metal interconnect structure includes a diffusion barrier layer formed on the side and bottom surfaces of the trench; and a metal layer formed on the diffusion barrier layer.
However, the interface between the ULK dielectric layer and the diffusion barrier layer has certain issues because the roughness of the ULK dielectric layer is relatively high. The relatively high roughness and porous nature of the ULK dielectric layer, especially when the ULK dielectric layer is damaged, may cause the metal atoms of the metal layer to penetrate into the ULK dielectric layer. Thus, the electric performance and reliability of the metal interconnect structure may be degraded.
The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.